All measured spectra were fit with the same accuracy. Figure REF  shows exemplary spectra acquired at \(\theta = 55^{\circ }\)  and their best fits with a Cody-Lorentz model. Figure REF  shows the reconstructed coating optical constants, and Figure REF  is a Cody plot highlighting the coating energy gap, \(E_g = 4.1 \pm 0.1\)  eV, which is consistent with that of pure tantala coatings produced under strictly identical conditions [1]}.
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